hello all.
total noob to networking, but not entirely to unix (no expert either).

after all the reading i've done (Complete FreeBSD, Linux Network Admin, OpenBSD online manual, man pages, web how-tos), i still can't grok the routing i want for my first network.

here is a simple setup with extra computers removed for simplicity. i'm using static ips because dhcp didn'tseem necessary (fixed set of computers; am i wrong)?

i've attached a txt diagram of my landscape.

as may be apparent, i intend to use openbsdbox as a gateway/firewall/nat/yaddayadda

the box talks to the internet fine (i can ssh into it).
rl0 is up.
i haven't messed with the wifi part of this yet (laptop1).

at this point i just want desktop1 to talk to openbsdbox (in an attempt to keep my learning process simple; after that i guess i'll turn on packet forwarding so desktop1 can reach the internet). in my reading, i see information which conflicts (only in my mind i know).

1.WHICH of the ips listed above do i set to default gateway?
2. What is the minimum set of routes i add to get desktop1 to talk to openbsdbox?

i usually don't ask to be spoon fed answers, especially on this since i'm really trying to learn the guts of unix, but i've been beating my head against a wall for a week trying to learn networking so i can get this set up, and something's eluding me.

Welcome! It's been awhile for me on this forum but I got the message and love helping with networking noobs interested in OBSD... so here goes.

Attached is the diagram you submitted with my changes. Let's review some changes and other points here-

trendnet should bridge, not route
Introducing multiple routed hops in a small lan should be avoided, and the wireless switch should be used for just that- wireless switching. Allow the OBSD box to be the router for the network. Later down the road this will lay the foundation for further securing your wireless internet access in your LAN (let's call that chapter 2).

The wireless switch can still maintain it's addressing...
So that it can have a placeholder address for management purposes, but that will need to change from the 192.168.10.0/24 it's currently showing as being assigned to in your original diagram to the 192.168.0.0/24 network that the desktops and the OBSDbox belong to.

default gateway for desktops should be 192.168.0.120
This is your rl0 interface that directly attaches to the Trendnet wireless switch (I know, it's a router, but we are just going to use it as a wireless switch between your desktop and your OBSDbox).

obsd box should nat between the 192.168.0.0/24 and 10.0.0.0/24
This will require not only a bit of learning/work in pf (which we can assist in, of course) but will also require turning on forwarding in the OBSDbox (# sysctl net.inet.ip.forwarding=1 or permanently edit /etc/sysctl.conf)

cradlepoint will of course nat between public and 10.0.0.0/24
The way you had the whole network using the 192.168.0.0/24 made it a flat network, but we want a routed breakpoint in the network to allow for NAT. That means the cradlepoint will need to speak to the OBSDbox on a different private network than the OBSDbox uses to talk to the desktops across the wireless switch.

don't worry about dhcp for now,
but there are some really good reasons to use it in your network

I'm sure I've left something out, but this should get you started. Remember to reference the diagram I attached back with the changes.

Code:

desktop1 laptop1
192.168.0.201 192.168.0.202
| |
|_192.168.0.2_________|
|
|
TRENDnet (wireless router)- USE AS A BRIDGE ONLY, NOT AS A ROUTER.
192.168.0.1
|
|
+-----rl0 192.168.0.120-----+ (ip i assigned)
| |
| openbsdbox |
| |
+-----dc0 10.0.0.110------+
|
|
cradlepoint (mobile broadband to ethernet converter)
10.0.0.1
|
|
internet
The default gateway of your desktops should be 192.168.0.120
The TRENDnet should bridge, not route, packets from desktop to obsdbox
Obsdbox should nat between the two private networks (192.168.0.0/24 and
10.0.0.0/24) unless the cradlepoint will have routing intelligence back
to the 192.168.0.0/24 network.